Report: Some Boulder city offices could not withstand 100-year flood

Ethan Daniel prepares a hot dog for a customer at Mustard's Last Stand in Boulder on Monday. The restaurant is housed in downtown Boulder's Park Central building, which a new city report says would not withstand a 100-year flood.
(
Mark Leffingwell
)

Boulder will hold an ideas competition for the Civic Area Master Plan, with entries due Jan. 11. Interested participants can sign up now for webinars on Dec. 20 or Dec. 27. To learn more about the competition, visit tinyurl.com/ctx2kqa.

Two of Boulder's city office buildings would not withstand a 100-year flood and the large amount of parking near Boulder Creek could endanger lives in a flash flood, according to a new analysis conduced as part of the Civic Area Master Plan development.

City officials are in the process of developing a Civic Area Master Plan that will guide the future of the area between Ninth and 17th streets and between Canyon Boulevard and Arapahoe Avenue. As part of that process, they are studying flood risk along Boulder Creak and current and future government office space needs because so many city buildings are within the planning area.

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The City Council will discuss the flood risk analysis and other elements of the planning process, including an upcoming ideas competition, at its meeting Tuesday night.

Some ideas for the area have included a science museum, a performing arts complex or an indoor, year-round Farmer's Market.

City staffers are recommending that Boulder come up with a plan to phase out use of the Park Central and New Britain office buildings, located along Boulder Creek near the intersection of Arapahoe and Broadway. In addition to city offices, the Park Central building houses the Mustard's Last Stand restaurant.

"We have concluded that the buildings as constructed are not able to withstand the 100-year flood event," consultants at Anthem Structural Engineering wrote in a report to the city. "Based on the flood and soil parameters for the site, the foundations of both buildings would be undermined due to scour, which would result in the collapse of the structures."

Scour occurs when swiftly moving flood waters remove sediment from around bridge abutments or other structures.

The consultants said the improvements necessary to make the buildings able to withstand a 100-year flood would cost more than 50 percent of the structures' current market value.

There also are 13 scattered parking lots throughout the Civic Area with almost 600 parking spaces for the West Senior Center, the Boulder Public Library, city offices and the Farmers Market, according to a city memo on the flood risks.

"The majority of deaths as a result of flash floods are due to people attempting to drive their vehicles out of the flooded areas," the memo said. "Cars, when swept downstream by flood waters, also create a significant hazard."

In the memo, city staffers recommend reconfiguring or relocating some of the surface parking spaces, especially those in the high-hazard flood zone.

Though it has been decades since there was a significant flood in downtown Boulder, the area represents one of the highest flash-flood risks in the state.

City officials said they plan to explore a number of options to phase out use of the downtown office buildings and find new parking, but details about those options were not available Monday.